1. Field of the Invention
The invention relates to bottles, jars, and more specifically to plastic closures for use on internally pressurized beverage bottles. Also disclosed is a bottle finish complimentary to the closure.
2. Description of the Prior Art
Beverage bottles have often been capped by metal "crown" clossures requiring a mechanical lifter for removal. The corresponding bottle finish employs a smooth bead at the bottle mouth and extending radially to the side thereof. The metal cap is crimped over the bead and is mechanically expanded during removal. The common structure is useful for retaining the pressure of carbonated beverages within the bottle. A major problem is that the cap cannot be reused after removal and presents a source of litter.
Other metal closures, known as "twist-off" caps, are hand twistable for removal but otherwise are quite similar to the above mentioned crown bottle caps. The corresponding bottle finish is equipped with short upwardly spiraling threads that extend for one-fourth to one-third of the circumferential distance around the bottle mouth. This type of closure is commonly used on non-returnable bottles, since the finish is far less durable than the type employing a smooth bead. The threads are easily damaged, as is the thinner bottle lip. This type of bottle is often objected to as being a source of litter.
Still other metal closures fully screw-on and off the bottles, and the finish is threaded to accomodate them. These threads also lack durability.
One of the most desirable solutions to the problems of metal closures is to construct the closure from a plastic that would allow the bottle to be resealed and would provide improved protection for the bottle finish. Many plastic closures have been proposed in the prior art, but the inherent flexibility of most plastics results in blow-off of such caps under the internal pressures generated by most carbonated soft drinks, beers and ales. To overcome this problem, plastic caps have now been made that incorporate an inner skirt that enters the bottle mouth to pressure seal the contained beverage. Other advances include an outer strengthening collar for holding the closure on the bead of the finish. Still other plastic closures have combined the features of screwing completely onto the bottle for a tight fit while employing an inner skirt for added pressure seal. In short, known plastic caps follow the design concepts of the older metal crown caps and screw-on caps, but the limitations of plastic materials have not yet allowed creating of a "twist-off" style plastic closure.
The advantages of a twist-off plastic closure include ease of use, low torque removal, reuseability, recycleability, better protection for the bottle finish, more gentle application to the bottle finish, less possibility of injuring the user's hand during removal, less possibility of injuring others if carelessly discarded, and a potential for biodegradability. Yet, another and completely unexpected advantage is that the use of plastic closures allows the creation of a completely new type of bottle finish that is far more durable than known twist-off or screw-on bottle finishes. Consequently, the twist-off feature can be applied to returnable and recycleable bottles where it was not practical to do so with metal closures. Such a new bottle finish can have a durability that compares with the bead finish used with the traditional metal crown cap.
These advantages and others reside in the invention, as described below.